The transcriptional coactivator PGC-1alpha plays a central role in lipid metabolism;although its specific regulatory functions have been extensively studied, not much is known about the identity of potential interacting molecules that could act as coregulators and switch on/off its activity in response to metabolic cues. We have undertaken a biochemical approach followed by mass spectrometry and recently characterized a novel PGC-1alpha binding molecule that is able to enhance PGC-1alpha's transcriptional activity in vitro. We are currently performing gain-and loss-of-function experiments assessing the effects of this novel cofactor on the expression of genes regulated by PGC-1alpha and we are determining its overall effects on lipid beta-oxidation in vivo.